Isoreticular Tuning of Conductive Metal-Organic Framework Nanocrystals for the Rapid Detection and Differentiation of Toxic Gases.

Despite advances in gas sensing technologies, achieving rapid detection and differentiation of toxic gases remains a critical challenge. Herein, three conductive metal-organic frameworks (cMOFs) based on metallotetrapyrazinoporphyrazine (MTPz) ligands are utilized to enable distinct chemiresistive sensing toward hazardous gases within seconds of exposure. This study focuses on harnessing variations in material-analyte interactions upon tuning the central metal within MTPz ligand (M = Co, Ni, Cu), to achieve discrete sensing responses capable of identifying hydrogen sulfide (H2S), ammonia (NH3), sulfur dioxide (SO2), and nitric oxide (NO), with detection limits as low as 0.7, 0.6, 2.5, and 0.03 ppm, respectively, within 6 seconds of gas exposure. The sensor array differentiates these gases at concentrations exceeding their permissible exposure limits within seconds. Complementary in situ and ex situ spectroscopic analyses reveal distinct redox processes governing the varied sensing responses, underscoring the critical role of molecular design in optimizing performance. This work establishes a framework for tailoring molecular design strategies toward next-generation gas sensing materials.